Cortisol Responsiveness to Insulin-induced Hypoglycemia in Cushing's Syndrome with Huge Nodular Adrenocortical Hyperplasia

Abstract

A 51-yr-old male patient with a 3yr history of Cushing's syndrome is described. The baseline plasma cortisol level was elevated, while the plasma ACTH levels remained at an undetectable level. Dynamic testing of pituitaryadrenal function revealed no suppression after 8mg of dexamethasone, and there was no response to metyrapone or CRF, while plasma cortisol showed a hyperresponse to synthetic ACTH. Plasma cortisolresponded to insulininduced hypoglycemia without an obvious ACTH response. These and the computerized tomography data suggested a “huge” bilateral nodular adrenocortical hyperplasia which was later confirmed by surgery, The left and right adrenal glands weighed 55 and 76g, respectively. In vitro experiments, using the adrenal tissue, showed that there was an adrenal cortisol response to 1-39 ACTH but not to regular insulin, arginine vasopressin, angiotensin II, norepinephrine or epinephrine. These results indicate that plasma cortisol responded to a slight hypoglycemia-induced plasma ACTH change which not detected in the ACTH radioimmunoassay or to factors other than ACTH which might be induced by hypoglycemia. © 1986, The Japan Endocrine Society. All rights reserved.